SYNTHESIS, RESOLUTION, AND ABSOLUTE-CONFIGURATION OF OPTICALLY PURE 5,5''-DIHYDROXY-4',4''',7,7''-TETRAMETHOXY-8,8''-BIFLAVONE AND ITS DERIVATIVES

Optically pure 5,5 ''-dihydroxy-4,4''',7,7 ''-tetramethoxy-8,8 ''-biflavone (1) and its dimethyl derivative 5 were synthesized for the first time. Resolution of the racemic (+/-)-1, prepared by a modified literature procedure, was performed via the formation and recrystallization of its (+)- and (-)-camphorsulfonate 6. Hydrolysis of the (+)- or (-)-camphorsulfonate 6 afforded optically pure (+)- or (-)-1, which was then methylated to give (+)- or (-)-5. The absolute configurations of(+)-1 and (-)-1, assigned as (aR) and (aS), respectively, were confirmed in an unambiguous manner by X-ray single crystal analysis and from their CD spectra.